Dark matter-electron scattering in dielectrics

A number of direct detection experiments are searching for electron excitations created by the scattering of sub-GeV dark matter. We present an alternate formulation of dark matter-electron scattering in terms of the dielectric response of a material. For dark matter which couples to electrons, this approach automatically accounts for in-medium screening effects, which were not included in previous rate calculations for semiconductor targets. We show that the screening effects appear for both scalar and vector mediators. The result is a non-negligible reduction of reach for direct detection experiments which use dielectric materials as targets. We also explore different determinations of the dielectric response, including first-principles density functional theory (DFT) calculations and a data-driven analytic approximation using a Mermin oscillator model.

Automated summary

The paper introduces an alternative formulation for dark matter-electron scattering that takes into account in-medium screening effects automatically. It demonstrates a significant reduction in reach for direct detection experiments using dielectric materials as targets. The study also explores different determinations of the dielectric response.